20 



the same, the observed weights must be corrected by the above 

 table in the following manner : 



Found, weight of empty bottle 15.235 



" " bottle -H water at 18° C 46.327 



Weight of water at 18° C 31.092 



"Weight of bottle f milk at 16° C 47.226 



" " " empty.. 15.235 



Weight of milk at 16° C 31.991 



The water having been weighed at 18° C, we have to deter- 

 mine the quantity of water required to fill the flask at 16° C. The 

 respective specific gravities of water are : 



At 18° C, 0.998817 ; at 16° C, 0.999155. 



The weight of the water required to fill the flask at 16° C. is, 

 therefore, 



0.998817: 31.092 = 0.999155 : X 

 X = 31.102 grs. 



31.991 



The specific gravity of the milk is, therefore, — 1.028. 



31.102 

 This is the specific gravity of the milk at 16° C, compared with 

 water at 16° C. 



Since the coefiidents of expansion of milk and water differ cer- 

 tainly not considerably, we can also consider the specific gravity of 

 this milk to be = 1.028 at 15° C, if compared with water of this 

 temperature. 



If once the contents of the flask are known, it is unnecessary 

 to repeat the weighing with water for each determination. It is 

 only necessary, from time to time, to examine the weight of the 

 flask, to ascertain whether it has not lost in weight by the removal 

 of small splinters of glass or by scratches. 



Lactodensimeter ; For ordihary determinations an areometer 

 or lactodensimeter may be employed to ascertain the specific 

 gravity. Quevenne's lactodensimeter is the most exact, and the 

 one most generally used. For description and use of this instru- 

 ment, we refer to the chapter treating on " Milk inspection." 



